I. Field of the Invention
The present invention relates generally to swing-frame auxiliary axle systems for load-hauling vehicles and, more particularly, to a system for attaching and operating the swing frame of a stowable tag axle that includes separate modular, adjustable, attachment and pivoting systems, also adaptable to deal with a range of different spacings between the main longitudinal truck chassis members for mounting. The swing frame also includes an improved modular operating cylinder mount system which also facilitates assembly and disassembly of this aspect.
II. Related Art
Optionally deployable swing-frame auxiliary axle systems are well known and often associated with a variety of types of load-hauling vehicles, particularly those accustomed to time-varying loading, such as dump trucks, refuse collection vehicles and transit concrete mixers. Such vehicles typically include a chassis or frame, a cab and a dedicated truck body mounted on the chassis behind the cab. Such vehicles also include a forward steering axle placed near the front of the cab and one or more sets of drive axles spaced behind the steering axle, the drive axles often being provided in a dual axle arrangement. The auxiliary axle systems furnish additional load carrying capacity by adding an axle for assisting the steering and drive axles in supporting the load and in adjusting the inter-axle distance or increasing the overall front-to-rear axle span distance for the vehicle. In this manner, not only does the tag axle system assist in balancing the load carried by, for example, a transit mixing cement truck, but generally it also enables the truck to carry a higher legal total payload than would otherwise be permitted because weight restrictions placed on vehicles traveling over highways are typically measured in terms of load per axle in combination with overall spacing between the vehicle axles.
Examples of such auxiliary axle assemblies that can be selectively engaged with the ground are shown, for example, in U.S. Pat. Nos. 5,897,123 and 5,018,755. Thus, it is known to have tag axle systems generally consisting of a rear tubular cross member carrying spaced wheel assemblies and carried by a pair of spaced tag axle arms which, in turn, are pivotally mounted to the rear portion of a truck chassis according to a generally known arrangement. Linear reciprocating operating devices, typically hydraulic cylinders, or pneumatic devices are employed to pivot the tag axle system between a raised or stowed position and a lowered or ground-engaging position.
The pivotal mounts for swing frames of the class typically have involved a rather cumbersome system for mounting the spaced tag axle arms in some fashion from the main longitudinal chassis frame or rail members using a plurality of flange members which typically carry a pivot pin member journaled in bushing or bearings carried in a housing fixed to or integral with each of the pivot arms. The pivot block brackets are typically welded or bolted to the chassis member and each pivot pin is typically assembled into inner and outer pivot blocks which consist of two halves which are bolted together to retain the pin, each block having a semi-circular groove therein. Since the bearing surface housing is an integral part of each pivot arm, the blocks must be disassembled to release the tag swing arms and the entire swing arm assembly must be replaced if the bearing surface in the housing becomes worn. With these disadvantages, it would present a great advance if the pivot joints of the swing-frame tag axle assembly could be made more independent of that assembly and independent of the truck chassis so that easy removal and replacement of a separate worn assembly could be accomplished.
Likewise, the operating cylinder for the swing-frame auxiliary axle system is typically mounted from a tag lever welded to the cross tube connecting and extending between the spaced parallel arms near the point of attachment to the chassis. The upper portion of the pivot arm or tag lever is provided with a pivotal mount similar to those for the swing arms to which the rod end of an operating cylinder is attached using a bearing assembly attached to the operating rod and carried on a pivot pin or shaft which, in turn, is attached to the tag lever by being carried by a spaced split block system. As was the case with the swing arm pivot joints, the operating cylinder cannot be disconnected from the auxiliary axle assembly without disassembly of the pair of pillows for the pivot pin and the lower pivot blocks of the block assemblies are welded to and an integral part of the pillow swing- frame assembly so that, as a practical matter, replacement of these lower blocks cannot be accomplished without replacement of the entire pivot frame assembly. Although, in this case, the bearing surface itself is not carried by the auxiliary tag axle frame but by the cylinder rod.
Typical assemblies for the pivoting connectors of the spaced arms of a swing-frame assembly are shown in FIG. 6 of U.S. Pat. No. 5,897,123 and a typical assembly for connecting the operating cylinder to the swing-frame pivot assembly is shown in FIG. 10 of that patent. To any extent necessary, that reference is deemed incorporated herein by reference in its entirety.
As was the case in the swing-frame pivot assemblies, the pivot assembly for attaching the rod end of the operating cylinder to the swing frame would be advantageously advanced were it made independent of or readily removable from the swing-frame pivot assembly. This would allow removal, repair and replacement of the wear parts of the system to be readily made without affecting the integrity of the truck chassis or swing-frame assembly of the auxiliary axle system.
Accordingly, it is a primary object of the present invention to provide a swing-frame pivot tag axle assembly in which the swing frame itself contains no pivot wear parts.
A further object of the present invention is to provide a swing-frame assembly for a tag axle system for connection to the chassis of a load-hauling vehicle in which no pivotal wear parts are permanently attached to the chassis of the vehicle.
A still further object of the present invention is to provide removable and replaceable pivot joints for both the swing-frame pivot assemblies and the operating cylinder of a swing-frame tag axle frame assembly.
Yet another object of the present invention is to provide a swing-frame tag axle mounting system which can be utilized with chassis rails of different separations.
Further objects, advantages and novel features of the present invention will become apparent from the detailed description of the invention, taken in conjunction with the accompanying claims and drawings.
Aspects of the present invention solve many long-standing problems associated with the construction and maintenance of swing-frame pivot assemblies for tag axle systems. The present invention enables the pivot joints for the swing frame and associated operating cylinder to be constructed as independent units with respect to both the swing frame and the truck chassis rails so that removal and replacement of worn parts does not require repair or replacement of the pivot frame itself or affect the mounting of the frame to the chassis rails. In the detailed embodiment of the invention which illustrates the basic principles and advantages of the invention, each of the arms of the swing-frame pivot assembly is attached to an associated main frame rail utilizing an independent system which includes a structural channel member or pivot bracket which includes a segment which aligns and uses locking fasteners or bolts to attach through a corresponding frame rail and also contains a pivot bearing housing aspect which extends just beyond the end of the frame rail. A pivot pin is mounted to rotate within the pivot bearing housing riding on a pair of spaced, lowfriction bushings which fit into opposite ends of the hollow housing and are flanked by protective washers. The end of each swing-frame arm is provided with a dual forkshaped connector which has top and bottom forked flanges designed to slip over the pivot pin. Clevis members are also provided between the dual forks and the pivot pin and holes through these members align with a slotted opening in each end of the pivot pin so that lateral adjustment of the arm is accommodated. Each arm of the swing-frame pivot assembly then mounts to the pivot pin utilizing a pair of through bolts, the pivot pin being designed to rotate inside the bushings as the corresponding arm of the swing frame pivots. In this manner, when wear or corrosion of a pivot joint occurs, the arm of the swing frame can be removed by simply removing or, if necessary, cutting of f the corresponding attaching bolts and the assembly can be removed from the chassis by simply unbolting the pivot bracket from the corresponding frame rail or removing the locking fasteners. To this end, high performance locking fasteners such as those available from Huck International, Inc. Industrial Fastener Division in Waco, TX, and known as xe2x80x9cHuckxe2x80x9d fittings may be used to connect to the frame rails so that they will not loosen, but these can be easily removed when desired.
Independent construction is also utilized with regard to the attachment of the operating or pivoting cylinder to the swing-frame pivot tag lever assembly in accordance with the invention. The rod end of the operating cylinder associated with the swing-frame pivot assembly of the invention is threadably attached to a hollow bearing sleeve into which are pressed spaced, oppositely disposed bushing devices, each having a central bore designed to accommodate a pivot pin journaled therein. These may be the same as those used for the pivot arm connections. The corresponding upper end of the pivot or tag lever assembly, the base of which is attached to the common torque tube of the swing-frame assembly, is provided with a mounting base member having pairs of spaced bolt holes therein. A pair of spaced bearing blocks are mounted on top of the mounting base member using removable bolts and nuts. As with the other assemblies, Huck fittings may be used. A removable pin spans the spaced bearing blocks capturing the hollow bearing sleeve therebetween. A two-piece, but preferably one-piece slotted bearing blocks are employed which, when tightened in place, fix the pivot pin in position. In operation, then, as the cylinder rod is operated linearly to raise, lower and adjust the pressure on the deployed tag axle, the bearing sleeve rotates about the fixed pivot pin supported on the spaced bushings.
Here, as in the case of the swing-frame pivot arm connections, disassembly for maintenance and replacement of worn and corroded parts is relatively simply. The simple removal of four bolts, even if cutting be necessary, frees the cylinder from the tag axle assembly even if the parts of the pivot joint are frozen. Likewise, removal of the hollow bearing sleeve from the rod end of the cylinder requires only unscrewing of the sleeve from the cylinder rod.
In this manner, all the pivot joints associated with the mounting and operation of the swing-arm pivot assembly are constructed independent from the joined structures. This greatly facilitates repair and replacement of worn and damaged parts.